Arlo, when you say an old car (to be honest 40+ years old is more than the 15-20 I was imagining) emits 50 or 130x more emissions I'm guessing you're talking about a specific trace emission like NoX or hydrocarbons. Those may be intolerable from the perspective of local air pollution, but I was sticking with CO2 since we're talking fuel consumption and energy which equal CO2 emission. Also, as pointed out above, EFI + catalytic converter (anything from approx. 1990 onwards) will be pretty clean of those toxic nasties.
My reference is only from an article in New Scientist (12th Dec 2015, pg. 37) that jumped out during casual reading. The article is by Fred Pearce, who by a cursory search doesn't appear to be a climate sceptic or denier (https://en.wikipedia.org/wiki/Fred_Pearce). The article says:
"If your current car was manufactured a decade ago, it might typically pump out about 1.8 tonnes of CO2 a year, if you drive an average of 12,000km. If you were to buy the most fuel efficient model you can find on garage forecourts today and drive a similar sort of distance, you'd emit about 1 tonne annually, according to company-declared emissions at least"
On embodied energy:
"According to manufacturers' figures the process of making a car typically takes between 600 and 800kg of CO2. Factor in making the steel for the body itself and you can add in another tonne of emissions. Add in the carbon footprint of the aluminium components - which require five times more energy to smelt than steel - plus upholstery, glass, rubber and electronics and your new car clocks in at around 6 tonnes of CO2, according to the UK's Carbon Trust. You'll have to run it for 8 years to recoup its carbon cost".
Playing with the 260 gallons to make a car figure, burning a 6.3lb gallon of gasoline apparently produces 20 lb of CO2. 20 x 260 = 5200lb / 2.2 = ~2.4 tonnes. They're clearly counting more than just the emissions for assembly, and at 3000lb (1.36 tonne) it's similar to the averageish European car, but clearly something is much different.
Anyway, does my take on it conveniently justify my continuing to run an older car rather than madly indebting myself to buy a new one? Yes, that's occurred to me before
